Carpal tunnel syndrome caused by supernumerous lumbrical muscle in hemihyperplasia of the upper extremity

Introduction. - Hemihyperplasia of the upper extremity is a rare pathology that occurs in 1/86,000 births. Carpal tunnel syndrome may be associated with this disease. Clinical presentation. - We describe the case of a 74-year-old male who has hemihyperplasia of both upper extremities since birth. At the age of 73, he started experiencing continuous, progressive and high intensity pain that occurred more frequently at night and was localized in the right hand. It was associated with paresthesia and hypoesthesia predominantly of the thumb, index finger and middle finger. Clinical examination and electrodiagnosis led to diagnosis of carpal tunnel syndrome. Results. - The patient underwent surgical carpal tunnel release to treat the disease. The enlarged nerve was compressed by a supernumerous lumbrical muscle, which was resected intraoperatively. After six months of follow-up the patient has normal sensitivity and grip strength in the right hand. Conclusion. - Hemihyperplasia should be clearly distinguished from other complex pathologies that may also entail CTS. Since significant variation in the anatomy of the hemihyperplasic extremities is the rule rather than the exception, a conventional open approach should be taken to localize and treat the compression. (C) 2012 Published by Elsevier Masson SAS.